The invention relates to a regenerative heat-exchanger having a rotor with peripheral, radially and axially sealed-off, heat storage banks, which can be utilized both in an air pre-heater and a gas pre-heater.
In the case of power plants and industrial furnaces, the flue gases are used in a regenerative heat exchanger for pre-heating of the combustion air. In this process, it is possible, for example, to reduce the nitrogen oxides (NO.sub.x) contained in the flue gas by a very considerable amount, by implementing, in this case, the heat storage banks in the regenerative heat exchanger as totally or partially effective catalytic elements and, above all, by introducing ammonia as the reducing agent. As a general rule, a flue gas containing nitrogen oxides is produced by a furnace and is used at the end of a steam generator for pre-heating of the combustion by flowing through the regenerative heat exchanger.
According to the present state of the art, as e.g., disclosed in the prospectus "Regenerative Heat Exchangers" of Lugat Aktiengesellschaft fur Luft and Gastechnik, Basel, in the case of regenerative heat exchangers with peripheral heat storage banks, the rotors and the rotor chambers or storage bank chambers are sealed off, both in the radial direction and in the axial direction, to prevent any possibility of mixing of one medium with the other, that is to prevent the possibility of mixing of the crude gas with the purified gas. Therefore, in the case of rotor seals with rotating heating surfaces, resilient metal sliding contact strips are provided. These strips are affixed to all of the radial walls and are adjusted in such a manner that they make sliding contact with radial spars of the heat exchanger housing. Additionally, there are metal sliding contact strips provided in the peripheral regions of both end surfaces of the rotor, which likewise make sliding contact with the rotor housing. The radial seals keep the media flowing through the heat exchanger separated from each other, and the peripheral seals allow to substantially avoid any bypass flow currents.
In the case of flue gas purification or reduction of noxious gases, large demands are made, at the present time to the individual components. Thus, for example, for a heat exchanger which, in a garbage incinerator plant, pre-heats the flue gas to the reaction temperature necessary for the catalytic purification, a leakage amount of significantly less than 0.3% is required in order to avoid emission of dioxin and furane. However, the known resilient sealing systems for a regenerative heat exchanger with peripheral heat storage banks cannot meet such requirements.